1. Field of the Invention
The present invention relates to a bearing and a liquid cooling type screw compressor using the bearing.
2. Description of the Related Art
In the screw compressor, a thrust load and a radial load are imposed on a rotor axis by gas compressed by a pair of male and female screw rotors meshing with each other. Therefore, the rotor axis is supported by a thrust bearing and a radial bearing. In order to reduce the load imposed on the above bearings so as to extend the life of the bearings, an apparatus for reducing the thrust load is proposed in Japanese Patent Publication No. Sho48-33041 and Japanese Patent Laid-Open No. Sho57-153986, and an apparatus for reducing the radial load is proposed in Japanese Patent Laid-Open No. Hei3-61714.
The screw compressor disclosed in Japanese Patent Laid-Open No. Hei3-61714 is configured such that a high pressure fluid chamber is provided on the side of the imposing direction of the radial load and a constant pressure fluid chamber is provided on the other side. In the case of the above screw chamber, width of bearings is large and hence the compressor has to be large.
In FIG. 9, provided that a load of axis weight W, the radial load, is imposed on an axis 101 from the top towards the bottom, a gap between a pressure receiving surface 103 of a bearing 102 and the axis 101 is partly narrowed, and oil is caught into the narrowed pressure receiving area A so that hydraulic pressure (dynamic pressure) Pd is generated as shown in FIG. 10. The above hydraulic pressure Pd is determined by oil viscosity, gap, rotation speed or the like and also determined by peripheral pressure P1. The peripheral pressure P1 is pressure of an end surface of the bearing 102. The more the hydraulic pressure is, the higher a load capacity of the bearing 102 is. However, the hydraulic pressure generated in the gap between the pressure receiving surface 103 of the bearing 102 and the axis 101 is higher than the periphery pressure P1 of the bearing 102. Therefore, as a result of leaking from the bearing gap to the end surface of the bearing, the load capacity is decreased.